The goal of this project is to reconstruct human Type 1 diabetes in a mouse model system. This goal will be accomplished through the achievement of two specific aims. First, we will develop optimized immunodeficient mice that will provide an ideal vessel for the three human tissue types most relevant to T1D, namely the hematopoietic system, the thymus, and pancreatic beta-cells. These mice will be tested and validated using human fetal tissues. Second, we will generate each of the three tissue types listed above using directed differentiation of induced pluripotent stem cells derived from a panel of T1D patients. These T1D tissues will be implanted in the immunodeficient mice, and the mice will be monitored to observe the onset of autoantibody production and autoimmune destruction of beta-cells. This mouse model of human T1D will allow, for the first time, a detailed analysis of the development of autoimmunity in real time, thus opening the possibility of identifying novel therapeutic avenues for the treatment of the disease. This system will also be used to test the relative contributions of various risk alleles and environmental factors to the emergence of the T1D phenotype. The novel mouse strains and directed differentiation protocols developed as part of this project will be of great use not only for the study of T1D, but will be of broad use for the study of immunology and transplantation medicine across many diseases. PUBLIC HEALTH RELEVANCE: This research will identify new ways to treat Type 1 diabetes. In addition to this, new strains of mice will be developed over the course of the project that will be of great use to a large community of researchers studying human immunology. Also as a part of this project, new methods will be developed to convert induced pluripotent stem cells into clinically useful cell types, such as blood cells and insulin-producing beta- cells, which could ultimately be transplanted into patients lacking those cells due to injury or disease.